Scents used for hunting come in many forms. Burnable incense type, solid waxy sticks applied by rubbing, dryer sheets used in a clothes dryer to scent clothing, powders sprayed into the air, and small solid wafers are some of the more recent developments. Probably the oldest and most widely used form of hunting scent is liquid. These liquid scents are derived both naturally and synthetically. Some come in highly concentrated forms. Attracting scents that smell like the animal's preferred foods are readily available, with acorn and apple scents being popular for deer hunting. Sexual attractants are used to lure males during the breeding season. These sexual attractant scents are formulated from fluids such as the urine of a female in its estrus cycle. Deer, moose and elk all respond to these scents during breeding season. Masking scents are often used along with attractants to mask a hunter's scent from the quarry's keen sense of smell. These can be applied directly to the hunter or distributed around the hunting site. There are scents available to make a hunter smell like everything from dirt to a skunk, with the effectiveness of a specific smell being a matter of opinion.
The concept of a venturi is that a gradual reduction or constriction in the cross section of a fluid flow channel causes a proportional increase in the velocity and kinetic energy of the flowing fluid, and a decrease in pressure in the constricted section of the channel. This phenomenon, described by Bernoulli's Principle, was first discovered by mathematician, physicist and physician Daniel Bernoulli of Switzerland, who died in 1782. An Italian physicist named G. B. Venturi, who died in 1822, also did research on this phenomenon. Venturi's invention of the Venturi-Tube is still used in various forms to measure the flow of fluids, and his name is most often attached to fluid flow channels of this shape or type. This age old science is still used today to adjust velocity and pressure in fluid flow channels.
A fluid can be defined as any substance, liquid or gas, that is capable of flowing and which changes its shape at a steady rate when acted on by a force. Air is a mixture of nitrogen, oxygen and other fluid gases that surround the earth to form its atmosphere. Air is a fluid that responds to the effects of the phenomenon described by Bernoulli's Principle.
A wind vane is defined as a device rotating freely in a horizontal plane and so mounted and formed as to point into the wind. Also referred to as weather vanes, these devices have been used for centuries to monitor wind direction and as alignment devices for windmills, turbines and pumps. Anywhere alignment to a flowing fluid is needed, a form of this device might be used.